Support setting WireMockServerSettings via Environment (#954)

* Support parsing environment variables (WireMockServerSettings__)

* case ignore

* fix

* SimpleSettingsParserTests

* .

* int

* more test

src/WireMock.Net/Extensions/DictionaryExtensions.cs

@@ -0,0 +1,29 @@
+using System.Collections;
+using System.Diagnostics.CodeAnalysis;
+using Stef.Validation;
+
+namespace WireMock.Extensions;
+
+internal static class DictionaryExtensions
+{
+    public static bool TryGetStringValue(this IDictionary dictionary, string key, [NotNullWhen(true)] out string? value)
+    {
+        Guard.NotNull(dictionary);
+        
+        if (dictionary[key] is string valueIsString)
+        {
+            value = valueIsString;
+            return true;
+        }
+
+        var valueToString = dictionary[key]?.ToString();
+        if (valueToString != null)
+        {
+            value = valueToString;
+            return true;
+        }
+
+        value = default;
+        return false;
+    }
+}